I have "played" with gum bichromate -- gum over cyanotype -- and love it. I was inspired by Sam Wang and Jim Larimer's work. I need the cyanotype layer to assist with registration as I don't yet have a large enough light box. Another bit of woodwork -- bad enough making the UV lamp box!

I live in Sydney (Chatswood) and would love to come to your exhibition. What is the venue and when does the exhibition start?

I measure the conditions with a handheld psychrometer before coating - I'm working at between 30% and 65% relative humidity and between 9°C and 15°C.
Cheers. B

I have had problems getting smooth even coating at temperatures lower than 20ºC. Also, if you can find Tween 20, it may help with those spots you're getting. It is a surfactant that helps get a smoother coating.

Since you're working with image setter negatives, they have a dot pattern. You need only find what the minimum exposure is for each color to get a strong tint through clear film.

My own personal method for development is to use three trays of standing water, not running water, at 10 minutes each. If the image hasn't developed to the right tint in that time, I adjust the exposure.

Thanks for the tips.
I have an old bottle of agfa wetter (agepon) which would probably do the same thing... Might try that. Cheers.
Do you think that adding what is in reality a detergent, changes development?
Are you brushing your layers with a foam brush or a hake? The quicker my layers go on the easier they are to smooth. Are you using a gum heavy emulsion? More gum = harder to smooth imho.

I've found that if I try to work with shorter exposures, and develop in around the time you're suggesting - even up to 1 hour, that the pigment runs while drying and I get ugly pigment stains. It seems that not enough is hardened onto the paper.
When I use a heavier exposure which develops over a longer period (2 to 2.5 hours) I get a cleaner result with no pigment runs.
I've calibrated my curves for heavy exposures - so I guess I can't change just now anyway

My second bath - the one that continually fills - is pretty close to still water. Its huge. 8ft by 5ft.

We're coming into warmer weather here in Sydney and I'm a little worried that my carefully worked out systems are going to fall to pieces in the higher temperatures and humidity...

Thanks for the tips - I'm just starting out with Gum Bichromate... trying to learn from books, which I'm not finding easy at all. Some of what you've said still means nothing to me, so I'm heading back to do some more research.

Well done for sticking at it Benjamin!

Try YouTube I found it is easier to see it than just read it. Found some good ideas for sizing and coating.

"Capturing an image is only one step of the long chain of events to create a beautiful Photograph See my updated website: mandersenphotography.com

Hi Bejamin, I have forgotten about this post, I'm sorry for not replying sooner. Gum printing is such a strange animal. Because I'm using continuous tone original camera negatives, no larger than 8 x 10, that may make a great difference in what works for me versus what works for you. But to answer a couple of your questions. I've tried lots of tried different brushes and rollers. I've settled on a 2 inch watercolor brush with synthetic bristles. Then I smooth out the coating with a goat hair brush similar to a hake. I mix equal parts of gum with potassium dichromate, or ammonium dichromate. I add and mix the pigment prior to adding adding the dichromate. The gum I use is typical artists gum, although I mixed my own from the crystals. It seemed to make no difference. I do get runoff into the borders sometimes, but I just ignore it. When communicating with the well known gum printer, Stephen Livick, he said after developing a print, he uses a heat gun to quick dry it and thus prevent runoff. Heat guns are used in paint stripping. Do you pre-size your paper?

Also, Livick said he doesn't like fluorescent tubes for gum. This prompted me to buy a 1000 watt metal halide plant light. It works fine, although the exposures are a bit longer. In an e-mail exchange with Keith Taylor, he said he uses a reversible dry mounting tissue. He detaches the print from the original aluminum sheet and then mounts it to a clean piece of the same Fabriano paper. I've seen his prints in galleries a number of times, they are quite beautiful, although if one looks closely, one can see the dot pattern.

Good luck to you. Gum printing can be very frustrating, but well worth the effort when you get what you hoped for.